Hiya,
Thought i'd update this thread now the car is all sorted. First thing I got checked was the O2 sensor as it is often this rather than the Cat. I got it replaced and reset the warning light but after another 200 miles it came back on
Nothing for it but getting a new cat.

Pricey but worth is as now as is well with the Insight again and she can get on with the imortant job of making me smile like a cheshire cat whenever I drive her..
o